<com.google.android.material.bottomnavigation.BottomNavigationView
...
app:itemIconSize="30dp"
/>
NOTE: Default icon size is 24dp
.
Edit res/values/dimens.xml
to avoid icon overlap with text.
<resources xmlns:tools="http://schemas.android.com/tools">
...
<dimen name="design_bottom_navigation_height" tools:override="true">60dp</dimen>
</resources>